Recently, application of carbon nanotubes (hereinafter referred to as CNTs) to various functional materials is specifically noted, as CNTs have excellent physical properties such as mechanical properties, optical properties and electric properties. In one field of such CNTs application, there is a strength-enhanced resin composite of which the lightweightness and the excellent mechanical strength are specifically noted; and the composite is expected to be applicable to many industrial materials of, for example, airplanes, automobiles, electronic parts, etc.
CNTs are known to be extremely excellent in mechanical properties such as tensile strength, Young's modulus of elasticity, etc. (e.g., see Non-Patent Document 1); and for producing CNTs-containing resin composites having excellent mechanical properties, preferably, the CNTs have a large specific surface area, the CNT content is high and the CNTs are aligned in a predetermined direction. The reasons for these are as follows: CNTs having a large surface area means that they are scarcely bundled and contain few impurities; and not only a resin could efficiently penetrate into the space between CNTs but also the area of the interface between the resin and CNTs increases, and therefore the power transmission efficiency between resin and CNTs can increase. Similarly, when the CNT content is high, then the area of the interface between resin and CNTs increases and the amount of CNTs having excellent mechanical properties increases, and therefore the mechanical strength of the CNTs-containing resin composite increases. Further, when CNTs are aligned, then the vector acting on CNTs can be controlled in the direction in which the strength of CNTs is the highest.
A CNTs-containing resin composite comprising CNTs and resin is proposed, which is produced by kneading CNTs in a matrix of an organic polymer such as a thermoplastic resin, a thermosetting resin a rubber, a thermoplastic elastomer or the like followed by applying a magnetic field in a predetermined direction to the resulting composition to thereby make the CNTs therein aligned in a predetermined direction and fixed in that state (see Patent Document 1).
However, CNTs have an extremely high aspect ratio and readily stick to each other by the van der Waals force, and therefore it is extremely difficult to align CNTs that are dispersed as unaligned in the initial stage in a highly viscous matrix, by post-treatment. In addition, CNTs have a low chemical activity and have an extremely low affinity to epoxy resins and others, and therefore it is difficult to produce a CNTs-containing epoxy resin composite having a high CNT content.
A method is proposed, which comprises injection-molding a CNTs-dispersed resin liquid to produce a fibrous CNTs-containing resin composite (see Patent Document 2). According to this, CNTs are aligned in the injection-molding step. Specifically, according to this, aligned CNT fibers having a high CNT content can be produced.
In this method, however, high-density aligned CNTs are introduced into a resin in the injection-molding step, and therefore only a fibrous CNTs-containing resin composite can be obtained in which CNTs are aligned in the machine direction. Specifically, even in this method, it is still impossible to control the alignment direction of CNTs in the CNTs-containing resin composite in a desired manner, and it is also impossible to produce a CNTs-containing resin composite having a desired shape in a simplified manner.
In other words, production of an aligned CNTs-containing resin composite taking the advantages of the anisotropic properties intrinsic to CNTs and having a high strength and a desired shape has heretofore been extremely difficult because of the above-mentioned situation.
On the other hand, the inventors of the present application have succeeded in obtaining greatly large-scaled CNTs aggregate of high alignment as compared with those in conventional methods, according to a method of chemical vapor deposition (hereinafter referred to as CVD) of CNTs in the presence of a metal catalyst in which a minor amount of water vapor is made to exist in the reaction atmosphere, and have reported it in Non-Patent Document 2. According to the method, CNTs aggregate of long aligned single-walled CNTs of high purity can be obtained, and these are expected to greatly contribute toward production of device materials, component materials, electroconductive materials, functional materials, etc. CNTs aggregate as referred to in this description means a structure of multiple CNTs (e.g., having nanotube density of at least 5×1011 nanotubes/cm3) as aggregated in the form of layers or bunches.    Non-Patent Document 1: M. F. Yu et al., Phys. Rev. Lett., 2000, 84, 5552    Non-Patent Document 2: Kenji Hata et al., Water-Assisted Highly Efficient Synthesis of Impurity-Free Single-Walled Carbon Nanotubes, SCIENCE, 2004, 11, 19, Vol. 306, pp. 1362-1364    Patent Document 1 JP-A 2002-273741    Patent Document 2: JP-A 2004-211239